91-18-18 MCDONNELL DOUGLAS: Amendment 39-8021. Docket No. 91-NM-175-AD. \n\n\tApplicability: Model DC-9-10, -20, -30, -40, -50, and C-9 (Military) series airplanes, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent rapid decompression of the pressurized fuselage, accomplish the following: \n\n\t(a)\tFor airplanes that have accumulated 55,000 landings or more as of the effective date of this AD, within 15 calendar days after the effective date of this AD, and thereafter at intervals not to exceed 1,500 landings, perform high frequency eddy current (HFEC) inspections to detect cracks of the fuselage left-hand skin panel at longeron 22L, between stations 160 and 200, in accordance with McDonnell Douglas Alert Service Bulletin A53-251, dated August 9, 1991. \n\n\t(b)\tFor airplanes that have accumulated less than 55,000 landings as of the effective date of this AD, within 45 calendar days after the effective date of this AD, or prior to the accumulation of 40,000 landings, whichever occurs later, and thereafter at intervals not to exceed 1,500 landings, perform high frequency eddy current (HFEC) inspections to detect cracks of the fuselage left-hand skin panel at longeron 22L, between stations 160 and 200, in accordance with McDonnell Douglas Alert Service Bulletin A53-251, dated August 9, 1991. \n\n\t(c)\tIf the fuselage skin attachments are obscured from exterior coatings of paint, prior to the accomplishment of the high frequency eddy current (HFEC) inspections required by paragraph (a) or (b) of this AD, chemically remove the obscuring coatings of paint. \n\n\t(d)\tIf cracks are found as a result of the inspections required by paragraph (a) or (b) of this AD, before further flight, repair in a manner approved by the Manager of the Los Angeles Aircraft Certification Office (ACO). \n\n\t(e)\tWithin 10 calendar days after the accomplishment of the initial inspections required by paragraph (a) or (b) of thisAD, submit a report of both positive and negative findings of the initial inspection to the Manager of the Los Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate, at 3229 East Spring Street, Long Beach, California 90806-2425, or Fax to (213) 988-5210. The information collection requirements contained in this regulation have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act of 1980 (P.L. 96-511) and have been assigned OMB Control Number 2120-0056. \n\n\t(f)\tIf other cracks, as specified in McDonnell Douglas Alert Service Bulletin A53-251, dated August 9, 1991, are found on any adjacent longerons or fuselage skin panels as a result of any other inspection of those areas, within 10 calendar days after those inspections, report all positive findings to the Manager of the Los Angeles ACO. The information collection requirements contained in this regulation have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act of 1980 (P.L. 96-511) and have been assigned OMB Control Number 2120-0056. \n\n\t(g)\tAn alternative method of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Los Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\tNOTE: The request should be forwarded through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Los Angeles ACO. \n\n\t(h)\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD. \n\n\t(i)\tThe inspection requirements shall be done in accordance with McDonnell Douglas Alert Service Bulletin A53-251, dated August 9, 1991. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C.552(a) and 1 CFR Part 51. Copies may be obtained from McDonnell Douglas Corporation, P. O. Box 1771, Long Beach, California 90846-0001, Attention: Business Unit Manager, Technical Publications, C1-HDR (54-60). Copies may be inspected at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington, or at the Los Angeles Aircraft Certification Office, 3229 East Spring Street, Long Beach, California, or at the Office of the Federal Register, 1100 L Street N.W., Room 8401, Washington, D.C. \n\n\tThis amendment (39-8021, AD 91-18-18) becomes effective on August 21, 1991.